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			<h1>C# <span class="color_h1">方法</span></h1>

<div class="tutintro">
<p>一个方法是把一些相关的语句组织在一起，用来执行一个任务的语句块。每一个 C# 程序至少有一个带有 Main 方法的类。</p>
<p>要使用一个方法，您需要：</p>
<ul class="list">
<li>定义方法</li>
<li>调用方法</li>
</ul>
</div>

<h2 class="tutheader">C# 中定义方法</h2>
<p>当定义一个方法时，从根本上说是在声明它的结构的元素。在 C# 中，定义方法的语法如下：</p>
<pre class="prettyprint">
&lt;Access Specifier&gt; &lt;Return Type&gt; &lt;Method Name&gt;(Parameter List)
{
   Method Body
}
</pre>
<p>下面是方法的各个元素：</p>
<ul class="list">
<li><b>Access Specifier</b>：访问修饰符，这个决定了变量或方法对于另一个类的可见性。</li>
<li><b>Return type</b>：返回类型，一个方法可以返回一个值。返回类型是方法返回的值的数据类型。如果方法不返回任何值，则返回类型为 <b>void</b>。</li>
<li><b>Method name</b>：方法名称，是一个唯一的标识符，且是大小写敏感的。它不能与类中声明的其他标识符相同。</li>
<li><b>Parameter list</b>：参数列表，使用圆括号括起来，该参数是用来传递和接收方法的数据。参数列表是指方法的参数类型、顺序和数量。参数是可选的，也就是说，一个方法可能不包含参数。</li>
<li><b>Method body</b>：方法主体，包含了完成任务所需的指令集。</li>
</ul>

<h2 class="tutheader">实例</h2>
<p>下面的代码片段显示一个函数 <i>FindMax</i>，它接受两个整数值，并返回两个中的较大值。它有 public 访问修饰符，所以它可以使用类的实例从类的外部进行访问。</p>
<div class="example"> 
<h2 class="example">实例</h2> 
<div class="example_code">

<span style="color: #6666cc; font-weight: bold;">class</span> NumberManipulator<br />
<span style="color: #008000;">&#123;</span><br />
&nbsp; &nbsp;<span style="color: #05a; font-weight: bold;">public</span> <span style="color: #6666cc; font-weight: bold;">int</span> FindMax<span style="color: #008000;">&#40;</span><span style="color: #6666cc; font-weight: bold;">int</span> num1, <span style="color: #6666cc; font-weight: bold;">int</span> num2<span style="color: #008000;">&#41;</span><br />
&nbsp; &nbsp;<span style="color: #008000;">&#123;</span><br />
&nbsp; &nbsp; &nbsp; <span style="color: #696969; font-style: italic;">/* 局部变量声明 */</span><br />
&nbsp; &nbsp; &nbsp; <span style="color: #6666cc; font-weight: bold;">int</span> result<span style="color: #008000;">;</span><br />
<br />
&nbsp; &nbsp; &nbsp; <span style="color: #05a; font-weight: bold;">if</span> <span style="color: #008000;">&#40;</span>num1 <span style="color: #008000;">&gt;</span> num2<span style="color: #008000;">&#41;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;result <span style="color: #008000;">=</span> num1<span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; <span style="color: #05a; font-weight: bold;">else</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;result <span style="color: #008000;">=</span> num2<span style="color: #008000;">;</span><br />
<br />
&nbsp; &nbsp; &nbsp; <span style="color: #05a; font-weight: bold;">return</span> result<span style="color: #008000;">;</span><br />
&nbsp; &nbsp;<span style="color: #008000;">&#125;</span><br />
&nbsp; &nbsp;<span style="color: #008000;">...</span><br />
<span style="color: #008000;">&#125;</span><br />

</div>
</div>

<h2 class="tutheader">C# 中调用方法</h2>
<p>您可以使用方法名调用方法。下面的实例演示了这点：</p>
<div class="example"> 
<h2 class="example">实例</h2> 
<div class="example_code">

<span style="color: #05a; font-weight: bold;">using</span> <span style="color: #696969;">System</span><span style="color: #008000;">;</span><br />
<br />
<span style="color: #05a; font-weight: bold;">namespace</span> CalculatorApplication<br />
<span style="color: #008000;">&#123;</span><br />
&nbsp; &nbsp;<span style="color: #6666cc; font-weight: bold;">class</span> NumberManipulator<br />
&nbsp; &nbsp;<span style="color: #008000;">&#123;</span><br />
&nbsp; &nbsp; &nbsp; <span style="color: #05a; font-weight: bold;">public</span> <span style="color: #6666cc; font-weight: bold;">int</span> FindMax<span style="color: #008000;">&#40;</span><span style="color: #6666cc; font-weight: bold;">int</span> num1, <span style="color: #6666cc; font-weight: bold;">int</span> num2<span style="color: #008000;">&#41;</span><br />
&nbsp; &nbsp; &nbsp; <span style="color: #008000;">&#123;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<span style="color: #696969; font-style: italic;">/* 局部变量声明 */</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<span style="color: #6666cc; font-weight: bold;">int</span> result<span style="color: #008000;">;</span><br />
<br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<span style="color: #05a; font-weight: bold;">if</span> <span style="color: #008000;">&#40;</span>num1 <span style="color: #008000;">&gt;</span> num2<span style="color: #008000;">&#41;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; result <span style="color: #008000;">=</span> num1<span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<span style="color: #05a; font-weight: bold;">else</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; result <span style="color: #008000;">=</span> num2<span style="color: #008000;">;</span><br />
<br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<span style="color: #05a; font-weight: bold;">return</span> result<span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; <span style="color: #008000;">&#125;</span><br />
&nbsp; &nbsp; &nbsp; <span style="color: #05a; font-weight: bold;">static</span> <span style="color: #6666cc; font-weight: bold;">void</span> Main<span style="color: #008000;">&#40;</span><span style="color: #6666cc; font-weight: bold;">string</span><span style="color: #008000;">&#91;</span><span style="color: #008000;">&#93;</span> args<span style="color: #008000;">&#41;</span><br />
&nbsp; &nbsp; &nbsp; <span style="color: #008000;">&#123;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<span style="color: #696969; font-style: italic;">/* 局部变量定义 */</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<span style="color: #6666cc; font-weight: bold;">int</span> a <span style="color: #008000;">=</span> <span style="color: Maroon;">100</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<span style="color: #6666cc; font-weight: bold;">int</span> b <span style="color: #008000;">=</span> <span style="color: Maroon;">200</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<span style="color: #6666cc; font-weight: bold;">int</span> ret<span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;NumberManipulator n <span style="color: #008000;">=</span> <span style="color: #008000;">new</span> NumberManipulator<span style="color: #008000;">&#40;</span><span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
<br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<span style="color: #696969; font-style: italic;">//调用 FindMax 方法</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;ret <span style="color: #008000;">=</span> n<span style="color: #008000;">.</span><span style="color: #05a;">FindMax</span><span style="color: #008000;">&#40;</span>a, b<span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;Console<span style="color: #008000;">.</span><span style="color: #05a;">WriteLine</span><span style="color: #008000;">&#40;</span><span style="color: #a11;">&quot;最大值是： {0}&quot;</span>, ret <span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;Console<span style="color: #008000;">.</span><span style="color: #05a;">ReadLine</span><span style="color: #008000;">&#40;</span><span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; <span style="color: #008000;">&#125;</span><br />
&nbsp; &nbsp;<span style="color: #008000;">&#125;</span><br />
<span style="color: #008000;">&#125;</span><br />

</div>
</div>
<p>当上面的代码被编译和执行时，它会产生下列结果：</p>
<pre class="result">
最大值是： 200
</pre>
<p>您也可以使用类的实例从另一个类中调用其他类的公有方法。例如，方法 <i>FindMax</i> 属于 <i>NumberManipulator</i> 类，您可以从另一个类 <i>Test</i> 中调用它。</p>
<div class="example"> 
<h2 class="example">实例</h2> 
<div class="example_code">

<span style="color: #05a; font-weight: bold;">using</span> <span style="color: #696969;">System</span><span style="color: #008000;">;</span><br />
<br />
<span style="color: #05a; font-weight: bold;">namespace</span> CalculatorApplication<br />
<span style="color: #008000;">&#123;</span><br />
&nbsp; &nbsp; <span style="color: #6666cc; font-weight: bold;">class</span> NumberManipulator<br />
&nbsp; &nbsp; <span style="color: #008000;">&#123;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; <span style="color: #05a; font-weight: bold;">public</span> <span style="color: #6666cc; font-weight: bold;">int</span> FindMax<span style="color: #008000;">&#40;</span><span style="color: #6666cc; font-weight: bold;">int</span> num1, <span style="color: #6666cc; font-weight: bold;">int</span> num2<span style="color: #008000;">&#41;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; <span style="color: #008000;">&#123;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <span style="color: #696969; font-style: italic;">/* 局部变量声明 */</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <span style="color: #6666cc; font-weight: bold;">int</span> result<span style="color: #008000;">;</span><br />
<br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <span style="color: #05a; font-weight: bold;">if</span> <span style="color: #008000;">&#40;</span>num1 <span style="color: #008000;">&gt;</span> num2<span style="color: #008000;">&#41;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; result <span style="color: #008000;">=</span> num1<span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <span style="color: #05a; font-weight: bold;">else</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; result <span style="color: #008000;">=</span> num2<span style="color: #008000;">;</span><br />
<br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <span style="color: #05a; font-weight: bold;">return</span> result<span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; <span style="color: #008000;">&#125;</span><br />
&nbsp; &nbsp; <span style="color: #008000;">&#125;</span><br />
&nbsp; &nbsp; <span style="color: #6666cc; font-weight: bold;">class</span> Test<br />
&nbsp; &nbsp; <span style="color: #008000;">&#123;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; <span style="color: #05a; font-weight: bold;">static</span> <span style="color: #6666cc; font-weight: bold;">void</span> Main<span style="color: #008000;">&#40;</span><span style="color: #6666cc; font-weight: bold;">string</span><span style="color: #008000;">&#91;</span><span style="color: #008000;">&#93;</span> args<span style="color: #008000;">&#41;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; <span style="color: #008000;">&#123;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <span style="color: #696969; font-style: italic;">/* 局部变量定义 */</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <span style="color: #6666cc; font-weight: bold;">int</span> a <span style="color: #008000;">=</span> <span style="color: Maroon;">100</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <span style="color: #6666cc; font-weight: bold;">int</span> b <span style="color: #008000;">=</span> <span style="color: Maroon;">200</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <span style="color: #6666cc; font-weight: bold;">int</span> ret<span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; NumberManipulator n <span style="color: #008000;">=</span> <span style="color: #008000;">new</span> NumberManipulator<span style="color: #008000;">&#40;</span><span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <span style="color: #696969; font-style: italic;">//调用 FindMax 方法</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; ret <span style="color: #008000;">=</span> n<span style="color: #008000;">.</span><span style="color: #05a;">FindMax</span><span style="color: #008000;">&#40;</span>a, b<span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Console<span style="color: #008000;">.</span><span style="color: #05a;">WriteLine</span><span style="color: #008000;">&#40;</span><span style="color: #a11;">&quot;最大值是： {0}&quot;</span>, ret <span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Console<span style="color: #008000;">.</span><span style="color: #05a;">ReadLine</span><span style="color: #008000;">&#40;</span><span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
<br />
&nbsp; &nbsp; &nbsp; &nbsp; <span style="color: #008000;">&#125;</span><br />
&nbsp; &nbsp; <span style="color: #008000;">&#125;</span><br />
<span style="color: #008000;">&#125;</span><br />

</div>
</div>
<p>当上面的代码被编译和执行时，它会产生下列结果：</p>
<pre>
最大值是： 200
</pre>

<h2 class="tutheader">递归方法调用</h2>
<p>一个方法可以自我调用。这就是所谓的 <b>递归</b>。下面的实例使用递归函数计算一个数的阶乘：</p>
<div class="example"> 
<h2 class="example">实例</h2> 
<div class="example_code">

<span style="color: #05a; font-weight: bold;">using</span> <span style="color: #696969;">System</span><span style="color: #008000;">;</span><br />
<br />
<span style="color: #05a; font-weight: bold;">namespace</span> CalculatorApplication<br />
<span style="color: #008000;">&#123;</span><br />
&nbsp; &nbsp; <span style="color: #6666cc; font-weight: bold;">class</span> NumberManipulator<br />
&nbsp; &nbsp; <span style="color: #008000;">&#123;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; <span style="color: #05a; font-weight: bold;">public</span> <span style="color: #6666cc; font-weight: bold;">int</span> factorial<span style="color: #008000;">&#40;</span><span style="color: #6666cc; font-weight: bold;">int</span> num<span style="color: #008000;">&#41;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; <span style="color: #008000;">&#123;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <span style="color: #696969; font-style: italic;">/* 局部变量定义 */</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <span style="color: #6666cc; font-weight: bold;">int</span> result<span style="color: #008000;">;</span><br />
<br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <span style="color: #05a; font-weight: bold;">if</span> <span style="color: #008000;">&#40;</span>num <span style="color: #008000;">==</span> <span style="color: Maroon;">1</span><span style="color: #008000;">&#41;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <span style="color: #008000;">&#123;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <span style="color: #05a; font-weight: bold;">return</span> <span style="color: Maroon;">1</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <span style="color: #008000;">&#125;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <span style="color: #05a; font-weight: bold;">else</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <span style="color: #008000;">&#123;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; result <span style="color: #008000;">=</span> factorial<span style="color: #008000;">&#40;</span>num <span style="color: #008000;">-</span> <span style="color: Maroon;">1</span><span style="color: #008000;">&#41;</span> <span style="color: #008000;">*</span> num<span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <span style="color: #05a; font-weight: bold;">return</span> result<span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <span style="color: #008000;">&#125;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; <span style="color: #008000;">&#125;</span><br />
&nbsp; &nbsp; <br />
&nbsp; &nbsp; &nbsp; &nbsp; <span style="color: #05a; font-weight: bold;">static</span> <span style="color: #6666cc; font-weight: bold;">void</span> Main<span style="color: #008000;">&#40;</span><span style="color: #6666cc; font-weight: bold;">string</span><span style="color: #008000;">&#91;</span><span style="color: #008000;">&#93;</span> args<span style="color: #008000;">&#41;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; <span style="color: #008000;">&#123;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; NumberManipulator n <span style="color: #008000;">=</span> <span style="color: #008000;">new</span> NumberManipulator<span style="color: #008000;">&#40;</span><span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; <span style="color: #696969; font-style: italic;">//调用 factorial 方法</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Console<span style="color: #008000;">.</span><span style="color: #05a;">WriteLine</span><span style="color: #008000;">&#40;</span><span style="color: #a11;">&quot;6 的阶乘是： {0}&quot;</span>, n<span style="color: #008000;">.</span><span style="color: #05a;">factorial</span><span style="color: #008000;">&#40;</span><span style="color: Maroon;">6</span><span style="color: #008000;">&#41;</span><span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Console<span style="color: #008000;">.</span><span style="color: #05a;">WriteLine</span><span style="color: #008000;">&#40;</span><span style="color: #a11;">&quot;7 的阶乘是： {0}&quot;</span>, n<span style="color: #008000;">.</span><span style="color: #05a;">factorial</span><span style="color: #008000;">&#40;</span><span style="color: Maroon;">7</span><span style="color: #008000;">&#41;</span><span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Console<span style="color: #008000;">.</span><span style="color: #05a;">WriteLine</span><span style="color: #008000;">&#40;</span><span style="color: #a11;">&quot;8 的阶乘是： {0}&quot;</span>, n<span style="color: #008000;">.</span><span style="color: #05a;">factorial</span><span style="color: #008000;">&#40;</span><span style="color: Maroon;">8</span><span style="color: #008000;">&#41;</span><span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Console<span style="color: #008000;">.</span><span style="color: #05a;">ReadLine</span><span style="color: #008000;">&#40;</span><span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
<br />
&nbsp; &nbsp; &nbsp; &nbsp; <span style="color: #008000;">&#125;</span><br />
&nbsp; &nbsp; <span style="color: #008000;">&#125;</span><br />
<span style="color: #008000;">&#125;</span><br />

</div>
</div>
<p>当上面的代码被编译和执行时，它会产生下列结果：</p>
<pre class="result">
6 的阶乘是： 720
7 的阶乘是： 5040
8 的阶乘是： 40320
</pre>

<h2 class="tutheader">参数传递</h2>
<p>当调用带有参数的方法时，您需要向方法传递参数。在 C# 中，有三种向方法传递参数的方式：</p>
<table class="reference notranslate">
<tr><th style = "width:30%">方式</th><th>描述</th></tr>
<tr><td>值参数</td><td>这种方式复制参数的实际值给函数的形式参数，实参和形参使用的是两个不同内存中的值。在这种情况下，当形参的值发生改变时，不会影响实参的值，从而保证了实参数据的安全。</td> </tr>
<tr><td>引用参数</td><td>这种方式复制参数的内存位置的引用给形式参数。这意味着，当形参的值发生改变时，同时也改变实参的值。</td> </tr>
<tr><td>输出参数</td><td>这种方式可以返回多个值。</td> </tr>
</table>

<h2>按值传递参数</h2>
<p>这是参数传递的默认方式。在这种方式下，当调用一个方法时，会为每个值参数创建一个新的存储位置。</p>
<p>实际参数的值会复制给形参，实参和形参使用的是两个不同内存中的值。所以，当形参的值发生改变时，不会影响实参的值，从而保证了实参数据的安全。下面的实例演示了这个概念：</p>
<div class="example"> 
<h2 class="example">实例</h2> 
<div class="example_code">

<span style="color: #05a; font-weight: bold;">using</span> <span style="color: #696969;">System</span><span style="color: #008000;">;</span><br />
<span style="color: #05a; font-weight: bold;">namespace</span> CalculatorApplication<br />
<span style="color: #008000;">&#123;</span><br />
&nbsp; &nbsp;<span style="color: #6666cc; font-weight: bold;">class</span> NumberManipulator<br />
&nbsp; &nbsp;<span style="color: #008000;">&#123;</span><br />
&nbsp; &nbsp; &nbsp; <span style="color: #05a; font-weight: bold;">public</span> <span style="color: #6666cc; font-weight: bold;">void</span> swap<span style="color: #008000;">&#40;</span><span style="color: #6666cc; font-weight: bold;">int</span> x, <span style="color: #6666cc; font-weight: bold;">int</span> y<span style="color: #008000;">&#41;</span><br />
&nbsp; &nbsp; &nbsp; <span style="color: #008000;">&#123;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<span style="color: #6666cc; font-weight: bold;">int</span> temp<span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;temp <span style="color: #008000;">=</span> x<span style="color: #008000;">;</span> <span style="color: #696969; font-style: italic;">/* 保存 x 的值 */</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;x <span style="color: #008000;">=</span> y<span style="color: #008000;">;</span> &nbsp; &nbsp;<span style="color: #696969; font-style: italic;">/* 把 y 赋值给 x */</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;y <span style="color: #008000;">=</span> temp<span style="color: #008000;">;</span> <span style="color: #696969; font-style: italic;">/* 把 temp 赋值给 y */</span><br />
&nbsp; &nbsp; &nbsp; <span style="color: #008000;">&#125;</span><br />
&nbsp; &nbsp; &nbsp; <br />
&nbsp; &nbsp; &nbsp; <span style="color: #05a; font-weight: bold;">static</span> <span style="color: #6666cc; font-weight: bold;">void</span> Main<span style="color: #008000;">&#40;</span><span style="color: #6666cc; font-weight: bold;">string</span><span style="color: #008000;">&#91;</span><span style="color: #008000;">&#93;</span> args<span style="color: #008000;">&#41;</span><br />
&nbsp; &nbsp; &nbsp; <span style="color: #008000;">&#123;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;NumberManipulator n <span style="color: #008000;">=</span> <span style="color: #008000;">new</span> NumberManipulator<span style="color: #008000;">&#40;</span><span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<span style="color: #696969; font-style: italic;">/* 局部变量定义 */</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<span style="color: #6666cc; font-weight: bold;">int</span> a <span style="color: #008000;">=</span> <span style="color: Maroon;">100</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<span style="color: #6666cc; font-weight: bold;">int</span> b <span style="color: #008000;">=</span> <span style="color: Maroon;">200</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;Console<span style="color: #008000;">.</span><span style="color: #05a;">WriteLine</span><span style="color: #008000;">&#40;</span><span style="color: #a11;">&quot;在交换之前，a 的值： {0}&quot;</span>, a<span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;Console<span style="color: #008000;">.</span><span style="color: #05a;">WriteLine</span><span style="color: #008000;">&#40;</span><span style="color: #a11;">&quot;在交换之前，b 的值： {0}&quot;</span>, b<span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<span style="color: #696969; font-style: italic;">/* 调用函数来交换值 */</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;n<span style="color: #008000;">.</span><span style="color: #05a;">swap</span><span style="color: #008000;">&#40;</span>a, b<span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;Console<span style="color: #008000;">.</span><span style="color: #05a;">WriteLine</span><span style="color: #008000;">&#40;</span><span style="color: #a11;">&quot;在交换之后，a 的值： {0}&quot;</span>, a<span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;Console<span style="color: #008000;">.</span><span style="color: #05a;">WriteLine</span><span style="color: #008000;">&#40;</span><span style="color: #a11;">&quot;在交换之后，b 的值： {0}&quot;</span>, b<span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;Console<span style="color: #008000;">.</span><span style="color: #05a;">ReadLine</span><span style="color: #008000;">&#40;</span><span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; <span style="color: #008000;">&#125;</span><br />
&nbsp; &nbsp;<span style="color: #008000;">&#125;</span><br />
<span style="color: #008000;">&#125;</span><br />

</div>
</div>
<p>当上面的代码被编译和执行时，它会产生下列结果：</p>
<pre>
在交换之前，a 的值：100
在交换之前，b 的值：200
在交换之后，a 的值：100
在交换之后，b 的值：200
</pre>
<p>结果表明，即使在函数内改变了值，值也没有发生任何的变化。</p>

<h2>按引用传递参数</h2>
<p>引用参数是一个对变量的<b>内存位置的引用</b>。当按引用传递参数时，与值参数不同的是，它不会为这些参数创建一个新的存储位置。引用参数表示与提供给方法的实际参数具有相同的内存位置。</p>
<p>在 C# 中，使用 <b>ref</b> 关键字声明引用参数。下面的实例演示了这点：</p>
<div class="example"> 
<h2 class="example">实例</h2> 
<div class="example_code">

<span style="color: #05a; font-weight: bold;">using</span> <span style="color: #696969;">System</span><span style="color: #008000;">;</span><br />
<span style="color: #05a; font-weight: bold;">namespace</span> CalculatorApplication<br />
<span style="color: #008000;">&#123;</span><br />
&nbsp; &nbsp;<span style="color: #6666cc; font-weight: bold;">class</span> NumberManipulator<br />
&nbsp; &nbsp;<span style="color: #008000;">&#123;</span><br />
&nbsp; &nbsp; &nbsp; <span style="color: #05a; font-weight: bold;">public</span> <span style="color: #6666cc; font-weight: bold;">void</span> swap<span style="color: #008000;">&#40;</span><span style="color: #05a; font-weight: bold;">ref</span> <span style="color: #6666cc; font-weight: bold;">int</span> x, <span style="color: #05a; font-weight: bold;">ref</span> <span style="color: #6666cc; font-weight: bold;">int</span> y<span style="color: #008000;">&#41;</span><br />
&nbsp; &nbsp; &nbsp; <span style="color: #008000;">&#123;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<span style="color: #6666cc; font-weight: bold;">int</span> temp<span style="color: #008000;">;</span><br />
<br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;temp <span style="color: #008000;">=</span> x<span style="color: #008000;">;</span> <span style="color: #696969; font-style: italic;">/* 保存 x 的值 */</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;x <span style="color: #008000;">=</span> y<span style="color: #008000;">;</span> &nbsp; &nbsp;<span style="color: #696969; font-style: italic;">/* 把 y 赋值给 x */</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;y <span style="color: #008000;">=</span> temp<span style="color: #008000;">;</span> <span style="color: #696969; font-style: italic;">/* 把 temp 赋值给 y */</span><br />
&nbsp; &nbsp; &nbsp; &nbsp;<span style="color: #008000;">&#125;</span><br />
&nbsp; &nbsp;<br />
&nbsp; &nbsp; &nbsp; <span style="color: #05a; font-weight: bold;">static</span> <span style="color: #6666cc; font-weight: bold;">void</span> Main<span style="color: #008000;">&#40;</span><span style="color: #6666cc; font-weight: bold;">string</span><span style="color: #008000;">&#91;</span><span style="color: #008000;">&#93;</span> args<span style="color: #008000;">&#41;</span><br />
&nbsp; &nbsp; &nbsp; <span style="color: #008000;">&#123;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;NumberManipulator n <span style="color: #008000;">=</span> <span style="color: #008000;">new</span> NumberManipulator<span style="color: #008000;">&#40;</span><span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<span style="color: #696969; font-style: italic;">/* 局部变量定义 */</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<span style="color: #6666cc; font-weight: bold;">int</span> a <span style="color: #008000;">=</span> <span style="color: Maroon;">100</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<span style="color: #6666cc; font-weight: bold;">int</span> b <span style="color: #008000;">=</span> <span style="color: Maroon;">200</span><span style="color: #008000;">;</span><br />
<br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;Console<span style="color: #008000;">.</span><span style="color: #05a;">WriteLine</span><span style="color: #008000;">&#40;</span><span style="color: #a11;">&quot;在交换之前，a 的值： {0}&quot;</span>, a<span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;Console<span style="color: #008000;">.</span><span style="color: #05a;">WriteLine</span><span style="color: #008000;">&#40;</span><span style="color: #a11;">&quot;在交换之前，b 的值： {0}&quot;</span>, b<span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
<br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<span style="color: #696969; font-style: italic;">/* 调用函数来交换值 */</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;n<span style="color: #008000;">.</span><span style="color: #05a;">swap</span><span style="color: #008000;">&#40;</span><span style="color: #05a; font-weight: bold;">ref</span> a, <span style="color: #05a; font-weight: bold;">ref</span> b<span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
<br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;Console<span style="color: #008000;">.</span><span style="color: #05a;">WriteLine</span><span style="color: #008000;">&#40;</span><span style="color: #a11;">&quot;在交换之后，a 的值： {0}&quot;</span>, a<span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;Console<span style="color: #008000;">.</span><span style="color: #05a;">WriteLine</span><span style="color: #008000;">&#40;</span><span style="color: #a11;">&quot;在交换之后，b 的值： {0}&quot;</span>, b<span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
&nbsp;<br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;Console<span style="color: #008000;">.</span><span style="color: #05a;">ReadLine</span><span style="color: #008000;">&#40;</span><span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
<br />
&nbsp; &nbsp; &nbsp; <span style="color: #008000;">&#125;</span><br />
&nbsp; &nbsp;<span style="color: #008000;">&#125;</span><br />
<span style="color: #008000;">&#125;</span><br />

</div>
</div>
<p>当上面的代码被编译和执行时，它会产生下列结果：</p>
<pre>
在交换之前，a 的值：100
在交换之前，b 的值：200
在交换之后，a 的值：200
在交换之后，b 的值：100
</pre>
<p>结果表明，<i>swap</i> 函数内的值改变了，且这个改变可以在 <i> Main</i> 函数中反映出来。</p>

<h2>按输出传递参数</h2>
<p>return 语句可用于只从函数中返回一个值。但是，可以使用 <b>输出参数</b> 来从函数中返回两个值。输出参数会把方法输出的数据赋给自己，其他方面与引用参数相似。</p>
<p>下面的实例演示了这点：</p>
<div class="example"> 
<h2 class="example">实例</h2> 
<div class="example_code">

<span style="color: #05a; font-weight: bold;">using</span> <span style="color: #696969;">System</span><span style="color: #008000;">;</span><br />
<br />
<span style="color: #05a; font-weight: bold;">namespace</span> CalculatorApplication<br />
<span style="color: #008000;">&#123;</span><br />
&nbsp; &nbsp;<span style="color: #6666cc; font-weight: bold;">class</span> NumberManipulator<br />
&nbsp; &nbsp;<span style="color: #008000;">&#123;</span><br />
&nbsp; &nbsp; &nbsp; <span style="color: #05a; font-weight: bold;">public</span> <span style="color: #6666cc; font-weight: bold;">void</span> getValue<span style="color: #008000;">&#40;</span><span style="color: #05a; font-weight: bold;">out</span> <span style="color: #6666cc; font-weight: bold;">int</span> x <span style="color: #008000;">&#41;</span><br />
&nbsp; &nbsp; &nbsp; <span style="color: #008000;">&#123;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<span style="color: #6666cc; font-weight: bold;">int</span> temp <span style="color: #008000;">=</span> <span style="color: Maroon;">5</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;x <span style="color: #008000;">=</span> temp<span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; <span style="color: #008000;">&#125;</span><br />
&nbsp; &nbsp;<br />
&nbsp; &nbsp; &nbsp; <span style="color: #05a; font-weight: bold;">static</span> <span style="color: #6666cc; font-weight: bold;">void</span> Main<span style="color: #008000;">&#40;</span><span style="color: #6666cc; font-weight: bold;">string</span><span style="color: #008000;">&#91;</span><span style="color: #008000;">&#93;</span> args<span style="color: #008000;">&#41;</span><br />
&nbsp; &nbsp; &nbsp; <span style="color: #008000;">&#123;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;NumberManipulator n <span style="color: #008000;">=</span> <span style="color: #008000;">new</span> NumberManipulator<span style="color: #008000;">&#40;</span><span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<span style="color: #696969; font-style: italic;">/* 局部变量定义 */</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<span style="color: #6666cc; font-weight: bold;">int</span> a <span style="color: #008000;">=</span> <span style="color: Maroon;">100</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;Console<span style="color: #008000;">.</span><span style="color: #05a;">WriteLine</span><span style="color: #008000;">&#40;</span><span style="color: #a11;">&quot;在方法调用之前，a 的值： {0}&quot;</span>, a<span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<span style="color: #696969; font-style: italic;">/* 调用函数来获取值 */</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;n<span style="color: #008000;">.</span><span style="color: #05a;">getValue</span><span style="color: #008000;">&#40;</span><span style="color: #05a; font-weight: bold;">out</span> a<span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
<br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;Console<span style="color: #008000;">.</span><span style="color: #05a;">WriteLine</span><span style="color: #008000;">&#40;</span><span style="color: #a11;">&quot;在方法调用之后，a 的值： {0}&quot;</span>, a<span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;Console<span style="color: #008000;">.</span><span style="color: #05a;">ReadLine</span><span style="color: #008000;">&#40;</span><span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
<br />
&nbsp; &nbsp; &nbsp; <span style="color: #008000;">&#125;</span><br />
&nbsp; &nbsp;<span style="color: #008000;">&#125;</span><br />
<span style="color: #008000;">&#125;</span><br />

</div>
</div>
<p>当上面的代码被编译和执行时，它会产生下列结果：</p>
<pre>
在方法调用之前，a 的值： 100
在方法调用之后，a 的值： 5
</pre>
<p>提供给输出参数的变量不需要赋值。当需要从一个参数没有指定初始值的方法中返回值时，输出参数特别有用。请看下面的实例，来理解这一点：</p>
<div class="example"> 
<h2 class="example">实例</h2> 
<div class="example_code">

<span style="color: #05a; font-weight: bold;">using</span> <span style="color: #696969;">System</span><span style="color: #008000;">;</span><br />
<br />
<span style="color: #05a; font-weight: bold;">namespace</span> CalculatorApplication<br />
<span style="color: #008000;">&#123;</span><br />
&nbsp; &nbsp;<span style="color: #6666cc; font-weight: bold;">class</span> NumberManipulator<br />
&nbsp; &nbsp;<span style="color: #008000;">&#123;</span><br />
&nbsp; &nbsp; &nbsp; <span style="color: #05a; font-weight: bold;">public</span> <span style="color: #6666cc; font-weight: bold;">void</span> getValues<span style="color: #008000;">&#40;</span><span style="color: #05a; font-weight: bold;">out</span> <span style="color: #6666cc; font-weight: bold;">int</span> x, <span style="color: #05a; font-weight: bold;">out</span> <span style="color: #6666cc; font-weight: bold;">int</span> y <span style="color: #008000;">&#41;</span><br />
&nbsp; &nbsp; &nbsp; <span style="color: #008000;">&#123;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Console<span style="color: #008000;">.</span><span style="color: #05a;">WriteLine</span><span style="color: #008000;">&#40;</span><span style="color: #a11;">&quot;请输入第一个值： &quot;</span><span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; x <span style="color: #008000;">=</span> Convert<span style="color: #008000;">.</span><span style="color: #05a;">ToInt32</span><span style="color: #008000;">&#40;</span>Console<span style="color: #008000;">.</span><span style="color: #05a;">ReadLine</span><span style="color: #008000;">&#40;</span><span style="color: #008000;">&#41;</span><span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; Console<span style="color: #008000;">.</span><span style="color: #05a;">WriteLine</span><span style="color: #008000;">&#40;</span><span style="color: #a11;">&quot;请输入第二个值： &quot;</span><span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; y <span style="color: #008000;">=</span> Convert<span style="color: #008000;">.</span><span style="color: #05a;">ToInt32</span><span style="color: #008000;">&#40;</span>Console<span style="color: #008000;">.</span><span style="color: #05a;">ReadLine</span><span style="color: #008000;">&#40;</span><span style="color: #008000;">&#41;</span><span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; <span style="color: #008000;">&#125;</span><br />
&nbsp; &nbsp;<br />
&nbsp; &nbsp; &nbsp; <span style="color: #05a; font-weight: bold;">static</span> <span style="color: #6666cc; font-weight: bold;">void</span> Main<span style="color: #008000;">&#40;</span><span style="color: #6666cc; font-weight: bold;">string</span><span style="color: #008000;">&#91;</span><span style="color: #008000;">&#93;</span> args<span style="color: #008000;">&#41;</span><br />
&nbsp; &nbsp; &nbsp; <span style="color: #008000;">&#123;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;NumberManipulator n <span style="color: #008000;">=</span> <span style="color: #008000;">new</span> NumberManipulator<span style="color: #008000;">&#40;</span><span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<span style="color: #696969; font-style: italic;">/* 局部变量定义 */</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<span style="color: #6666cc; font-weight: bold;">int</span> a , b<span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;<span style="color: #696969; font-style: italic;">/* 调用函数来获取值 */</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;n<span style="color: #008000;">.</span><span style="color: #05a;">getValues</span><span style="color: #008000;">&#40;</span><span style="color: #05a; font-weight: bold;">out</span> a, <span style="color: #05a; font-weight: bold;">out</span> b<span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
<br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;Console<span style="color: #008000;">.</span><span style="color: #05a;">WriteLine</span><span style="color: #008000;">&#40;</span><span style="color: #a11;">&quot;在方法调用之后，a 的值： {0}&quot;</span>, a<span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;Console<span style="color: #008000;">.</span><span style="color: #05a;">WriteLine</span><span style="color: #008000;">&#40;</span><span style="color: #a11;">&quot;在方法调用之后，b 的值： {0}&quot;</span>, b<span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;Console<span style="color: #008000;">.</span><span style="color: #05a;">ReadLine</span><span style="color: #008000;">&#40;</span><span style="color: #008000;">&#41;</span><span style="color: #008000;">;</span><br />
&nbsp; &nbsp; &nbsp; <span style="color: #008000;">&#125;</span><br />
&nbsp; &nbsp;<span style="color: #008000;">&#125;</span><br />
<span style="color: #008000;">&#125;</span><br />

</div>
</div>
<p>当上面的代码被编译和执行时，它会产生下列结果（取决于用户输入）：</p>
<pre class="result">
请输入第一个值：
7
请输入第二个值：
8
在方法调用之后，a 的值： 7
在方法调用之后，b 的值： 8
</pre>			<!-- 其他扩展 -->
						
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	<ol class="commentlist">
		<li class="comment even thread-even depth-1" id="comment-20512"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;StoneBelieve</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;756***808@qq.com</p></div><div id="runoobvote-id-20512" data-commid = "20512" class="upvotejs"><a class="upvote"></a> <span class="count">50</span></div></div><div class="comt-main" id="div-comment-20512"><p>局部变量是只能在函数内部访问到的，而字段可以在整个类中访问到,在外部声明可以在其他方法使用的时候进行调用，比如有另外一个方法想要调用max值即可直接使用；</p><pre>using System;

namespace CalculatorApplication
{
    class NumberManipulator
    {
        int max;
        public int FindMax(int num1, int num2)
        {
            /* 局部变量声明 */
            int result;

            if (num1 &gt; num2)
                result = num1;
            else
                result = num2;

            return result;
        }
        public  int getmax(int max)//该方法同样可以获取max中的值
        {
            return max;
        }
        static void Main(string[] args)
        {
            /* 局部变量定义 */
            int a = 100;
            int b = 200;
            NumberManipulator n = new NumberManipulator();

            //调用 FindMax 方法
            n.max = n.FindMax(a, b);
            Console.WriteLine("最大值是： {0}", n.max );
            Console.ReadLine();
        }
    }
}</pre><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">StoneBelieve</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;StoneBelieve</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;756***808@qq.com</p></div></span>6年前 (2017-11-19)</div></div></li><!-- #comment-## -->
<li class="comment odd alt thread-odd thread-alt depth-1" id="comment-21802"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;十一年话</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;142***5852@qq.com</p><p><i class="fa fa-external-link" aria-hidden="true"></i> <a rel="nofollow" target="_blank" href="https://zhidao.baidu.com/question/143813525.html">&nbsp;&nbsp;参考地址</a></p></div><div id="runoobvote-id-21802" data-commid = "21802" class="upvotejs"><a class="upvote"></a> <span class="count">120</span></div></div><div class="comt-main" id="div-comment-21802"><p><strong>ref 和 out 的区别</strong></p>
<p>一个用关键字 ref 标示，一个用 out 标示。</p>
<p>牵扯到数据是引用类型还是值类型。</p>
<p>一般用这两个关键字你是想调用一个函数将某个值类型的数据通过一个函数后进行更改。传 out 定义的参数进去的时候这个参数在函数内部必须初始化。否则是不能进行编译的。ref 和 out 都是传递数据的地址，正因为传了地址，才能对源数据进行修改。</p>
<p>一般情况下不加 ref 或者 out 的时候，传值类型的数据进去实际上传进去的是源数据的一个副本，也就是在内存中新开辟了一块空间，这里面存的值是与源数据相等的，这也就是为什么在传值类型数据的时候你如果不用 return 是无法修改原值的原因。但是你如果用了 ref,或者 out，这一切问题都解决了，因为他们传的是地址。</p>
<p>out 比起 ref 来说，还有一个用法就是可以作为多返回值来用，都知道函数只能有一个返回值，C#里，如果你想让一个函数有多个返回值，那么OUT能很容易解决。</p><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">十一年话</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;十一年话</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;142***5852@qq.com</p><p><i class="fa fa-external-link" aria-hidden="true"></i> <a rel="nofollow" target="_blank" href="https://zhidao.baidu.com/question/143813525.html">&nbsp;&nbsp;参考地址</a></p></div></span>5年前 (2017-12-19)</div></div></li><!-- #comment-## -->
<li class="comment even thread-even depth-1" id="comment-25262"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;heardwine</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;410***830@qq.com</p><p><i class="fa fa-external-link" aria-hidden="true"></i> <a rel="nofollow" target="_blank" href="http://blog.csdn.net/jl1134069094/article/details/50512103">&nbsp;&nbsp;参考地址</a></p></div><div id="runoobvote-id-25262" data-commid = "25262" class="upvotejs"><a class="upvote"></a> <span class="count">101</span></div></div><div class="comt-main" id="div-comment-25262"><h2>方法中参数的类型有三种
</h2>
<p><strong>in型参数 </strong></p>
int 型参数通过值传递的方式将数值传入方法中，即我们在Java中常见的方法。

<p><strong> ref型参数 </strong></p>
<p>该种类型的参数传递变量地址给方法（引用传递），传递前变量必须初始化。 </p>
<p>该类型与out型的区别在与：</p> <ul><li>
1）.ref 型传递变量前，变量必须初始化，否则编译器会报错, 而 out 型则不需要初始化 </li><li>
2）.ref 型传递变量，数值可以传入方法中，而 out 型无法将数据传入方法中。换而言之，ref 型有进有出，out 型只出不进。
 </li></ul>
<p><strong>out 型参数 </strong></p>
<p>与 ref 型类似，仅用于传回结果。 </p>
<p><strong>注意：</strong></p> 
<p>1). out型数据在方法中必须要赋值，否则编译器会报错。 </p>
<p>eg:如下图若将代码中的sum1方法的方法体 </p>
<p>改为 a+=b; 则编译器会报错。原因：out 型只出不进，在没给 a 赋值前是不能使用的 </p>
<p>改为 b+=b+2; 编译器也会报错。原因：out 型数据在方法中必须要赋值。 </p>
<p>2). 重载方法时若两个方法的区别仅限于一个参数类型为ref 另一个方法中为out，编译器会报错 </p>
<p>eg：若将下面的代码中将方法名 vsum1 改为 sum（或者将方法名 sum 改为 sum1），编译器会报错。 </p>
<pre>Error 1 Cannot define overloaded method &lsquo;sum&rsquo; because it differs from another method only on ref and out </pre>
<p>原因：参数类型区别仅限于 为 ref 与为 out 时，若重载对编译器而言两者的元数据表示完全相同。</p>
<pre>class C
{
    //1. in型参数
    public void sum(int a, int b) {
        a += b;
    }
    //2. ref型参数
    public void sum(ref int a, int b)
    {
        a += b;
    }
    //3. out型参数
    public void sum1(out int a, int b)
    {
        a = b+2;
    }
    public static void Main(string[] args)
    {
        C c = new C();
        int a = 1, b = 2;
        c.sum(a,b);
        Console.WriteLine("a:{0}", a);
        a = 1; b = 2;
        c.sum(ref a, b);
        Console.WriteLine("ref a:{0}", a);
        a = 1; b = 2;
        c.sum1(out a, b);
        Console.WriteLine("out a:{0}", a);
    }
}</pre>

<p>输出结果： </p>
<p><img src="//www.runoob.com/wp-content/uploads/2018/03/1521532063-6576-.png"></p>
<p>从代码也可以看出，int 型参数为值传递，所以当将变量 a 传入方法时，变量 a 的值并不会发生变化。而 ref 型参数，由于是引用传递，将变量的值和地址都传入方法中故变量值改变。out 型无法将变量的值传入。但可以将变量的地址传入并为该地址上的变量赋值。</p>
<div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">heardwine</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;heardwine</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;410***830@qq.com</p><p><i class="fa fa-external-link" aria-hidden="true"></i> <a rel="nofollow" target="_blank" href="http://blog.csdn.net/jl1134069094/article/details/50512103">&nbsp;&nbsp;参考地址</a></p></div></span>5年前 (2018-03-20)</div></div></li><!-- #comment-## -->
<li class="comment odd alt thread-odd thread-alt depth-1" id="comment-33429"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;Solitary</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;119***7522@qq.com</p></div><div id="runoobvote-id-33429" data-commid = "33429" class="upvotejs"><a class="upvote"></a> <span class="count">20</span></div></div><div class="comt-main" id="div-comment-33429"><p><strong>按值传递参数的问题：</strong></p>

<p>为什么即使在函数内改变了值，值也没有发生任何的变化呢？</p>
<pre>在交换之前，a 的值：100
在交换之前，b 的值：200
在交换之后，a 的值：100
在交换之后，b 的值：200</pre>
<p><strong>解析：</strong></p><p>调用一个方法时相当于复制一个对象到新分配的内存中，方法完毕对象也就del了，两个变量是不同的两个地址，a只不过是栈里的临时变量而已，和主函数里的变量没有关系，因此不会改变b的值。</p>

<p>而指针和引用直接访问内存地址，故直接修改所指向的对象，两者指向同一变量。</p><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">Solitary</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;Solitary</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;119***7522@qq.com</p></div></span>5年前 (2018-07-31)</div></div></li><!-- #comment-## -->
<li class="comment even thread-even depth-1" id="comment-34426"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;大軒</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;big***n@foxmail.com</p></div><div id="runoobvote-id-34426" data-commid = "34426" class="upvotejs"><a class="upvote"></a> <span class="count">41</span></div></div><div class="comt-main" id="div-comment-34426"><p><strong>扩展方法</strong></p>

<p>扩展方法可以实现在不需要修改目标类，也不需要继承目标类的情况下为其添加一个方法。</p>

<p><strong>规则：</strong></p>
<ul><li>
1、扩展类必须为静态类，扩展方法必须为静态方法。
</li><li>
2、扩展方法的第1个形参开头必须使用 “this” 关键字然后再填写扩展的目标类。
</li><li>
3、如果需要接收参数则从第2个参数开始算起，第1个参数在真正调用方法时是隐藏的。</li></ul>

<pre>public static class ExtensionString
{
    //向 String 类扩展一个统计单词数量的方法
    public static int CountWord(this String str)
    {
        return str.Split(' ').Length;
    }
}

class MainClass
{
    public static void Main(string[] args)
    {
        Console.WriteLine("单词数量:" + "Hello World".CountWord()); //没有参数
    }
}</pre><div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">大軒</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;大軒</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;big***n@foxmail.com</p></div></span>5年前 (2018-08-25)</div></div></li><!-- #comment-## -->
<li class="comment odd alt thread-odd thread-alt depth-1" id="comment-34538"><span class="comt-f">#0</span><div class="comt-avatar wrapper"><i style="font-size:36px;" class="fa fa-user-circle" aria-hidden="true"></i><div class="tooltip"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;信仰</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;cfe***ixin@qq.com</p><p><i class="fa fa-external-link" aria-hidden="true"></i> <a rel="nofollow" target="_blank" href="../w3cnote/c-array-as-parameter.html">&nbsp;&nbsp;参考地址</a></p></div><div id="runoobvote-id-34538" data-commid = "34538" class="upvotejs"><a class="upvote"></a> <span class="count">15</span></div></div><div class="comt-main" id="div-comment-34538"><p><strong>对于复杂引用类型参数传递的控制</strong></p><p>所谓复杂，是参数是数组或集合类型，或者参数包含这些类型数据，这种情况下上面的方法不能保证参数数据不被修改，因为即使对象为只读的，但是对象中的数组或集合字段（属性）还是可以修改的。</p><p><strong>1、集合参数（包含集合字段的引用参数也一样）</strong></p><p>.net 4.5以前版本可以使用不包含修改集合元素方法的接口来代替具体集合类型。例如使用IEnumerable&lt;T&gt;接口代替List&lt;T&gt;。4.5版本可以直接使用IReadOnlyCollection接口或实现该接口的集合类型。</p><p><strong>2、数组参数</strong></p><p>没有好的办法保护数组类型参数不被修改，所以尽量避免使用数组类型作为方法参数，除非用到可选参数时候。</p>


<blockquote><p>更多内容参考：<a href="../w3cnote/c-array-as-parameter.html" target="_blank" rel="noopener nofollow">C# 中数组作为参数传递的问题</a></p></blockquote>

<div class="comt-meta wrapper"><span class="comt-author"><a target="_blank" href="javascript:;">信仰</a><div class="tooltip tooltip1"><p><i class="fa fa-user" aria-hidden="true"></i>&nbsp;&nbsp;&nbsp;信仰</p><p><i class="fa fa-envelope" aria-hidden="true"></i>&nbsp;&nbsp;cfe***ixin@qq.com</p><p><i class="fa fa-external-link" aria-hidden="true"></i> <a rel="nofollow" target="_blank" href="../w3cnote/c-array-as-parameter.html">&nbsp;&nbsp;参考地址</a></p></div></span>5年前 (2018-08-29)</div></div></li><!-- #comment-## -->
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